TAILIEUCHUNG - Báo cáo khóa học: Hydrolytic cleavage by a group I intron ribozyme is dependent on RNA structures not important for splicing

DiGIR2 is the group I splicing-ribozyme of themobile twin-ribozyme intron in Didymiumnuclear ribosomal DNA. DiGIR2 is responsible for intron excision, exon ligation,3¢-splice site hydrolysis,and full-length intron RNA circle formation. We recently reported that DiGIR2 splicing (intron excision and exon ligation) competes with hydrolysis and subsequent full-length intron circularization. Herewe present experimental evidence that hydrolysis at the 3¢-splice site in DiGIR2 is dependent on structural elements within the P9 subdomain not involved in splicing | Eur. J. Biochem. 271 1015-1024 2004 FEBS 2004 doi Hydrolytic cleavage by a group I intron ribozyme is dependent on RNA structures not important for splicing Peik Haugen1 Morten Andreassen2 Asa B. Birgisdottir1 and Steinar Johansen1 2 1 Department of Molecular Biotechnology Institute of Medical Biology University of Troms0 Norway 2Faculty of Fisheries and Natural Sciences Bod0 Regional University Norway DiGIR2 is the group I splicing-ribozyme of the mobile twinribozyme intron present Id Didymium nuclear ribosomal DNA. DiGIR2 is responsible for intron excision exon ligation 3 -splice site hydrolysis and l ul l ength intron RNA circle formation. We recently reported that DiGIR2 splicing intron excision and exon ligation competes with hydrolysis and subsequent full-length intron circularization. Here we present experimental evidence that hydrolysis at the 3 -splice site in DiGIR2 is dependent on structural elements within the P9 subdomain not involved in splicing. Whereas the GCGA tetra-loop in P9b was found to be important in hydrolytic cleavage pi obttbly dee to 1 1 0 1 5 RNA RNA interactions toe hatspin tt Llcture was fondd to be essential for hydrolysis. The most important positions in include three adenosines in the terminal loop and a consensus kink-turn motif in the proximal stem. We suggest that the adenosines and the kink-motif represent key regulatory elements in the splicing and hydrolytic reaction pathways. Keywords Didymium iridis group I intron ribozyme hydrolysis RNA processing RNA structures. A highly conserved catalytic core is responsible for the self-splicing reactions of group I intron ribozymes 1 . The secondary structures of paired segments P1-P10 and the optional P11-P17 are organized into three-dimensional domains were P4-P6 and P3-P9 form the catalytic core 2 3 . The available crystal structure of the Tetrahymena intron ribozyme core reveals an active site preorganized to catalysis

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